1. Field of the Invention
The present invention relates to a technique for embodying a self-diagnosis function in an image formation device such as a facsimile reproduction machine, and more particularly, to a technique for sensing and reporting abnormalities in data received in a receiving mode or data scanned in a copy mode or transmitting mode.
2. Description of the Related Art
In image formation devices such as facsimile reproduction machines, a central processing unit controls the overall facsimile machine in accordance with a set program once one of a transmitting mode, a receiving mode or a copy mode has been set. A network control unit forms a speech path between a public subscriber's telephone network and a modem under the control of the central processing unit. The modem demodulates an analog signal received via the network control unit into a digital signal and modulates a digital signal from the central processing unit into an analog signal under the control of the central processing unit. A scanner scans a provided document once the transmitting or copy mode has been set to convert it into an image data and supplies the image data to the central processing unit. An operating panel consists of a key matrix equipped with a plurality of keys and provides key data produced by key manipulation to the central processing unit. A printer prints data received or desired to be duplicated under the control of the central processing unit. Additionally, a temperature detecting circuit is internally provided in the printer for sensing a surface temperature of a recording element contained within the printer so as to inform the central processing unit of the sensed temperature thereof. A memory stores received data for detecting a lack of recording paper while printing the document or for detecting the reception of black data or white data in a receiving mode and reads out the stored data under the control of the central processing unit.
The circuit for sensing the surface temperature of the recording element includes a thermistor which contacts the surface of the recording element and has a resistance value which is varied corresponding to the heat generated during the driving of the recording element. A supply voltage is divided in accordance with the resistance value of a resistor connected in series with the thermistor and the divided voltage is supplied to the central processing unit to monitor the overheating of the recording element. The voltage caused by the resistance value of the thermistor at a room temperature of the recording element furnished within the printer is utilized as a reference voltage. The recording element has its surface temperature raised when black data is being printed and becomes excessively heated when two or more pages of black data are successively printed to induce overheating. The overheating causes the central processing unit to block the driving of the recording element when the resistance value of the thermistor is continuously raised by the overheating of the recording element so as to supply a voltage which is higher than the preset value to the central processing unit.
First, the surface temperature of the recording element is sensed by means of the thermistor for preventing a black paper output (i.e., a continuous, solid dark image) in either a copy mode or receiving mode. In the operation of sensing the black paper output, the surface temperature of the recording element is raised when the black sheet of paper is provided for a prescribed period. The resistance value of the thermistor for sensing the temperature of the recording element is raised and the voltage due to the thermistor is increased due to the rising resistance value thereof. If the surface temperature of the recording element is raised due to overheating so as to be over a preset level so as to make the voltage due to the thermistor exceed a preset voltage, the operation of the recording element is inhibited to prevent the black paper output. When a black sheet of paper is provided, the receiving or copy mode is continuously performed until the voltage due to the thermistor reaches the preset voltage due to the overheating of the recording element. That is, the operation of the recording element is stopped only after two or more pages of black sheets have been printed.
The damage resulting from the overheating of the recording element can be prevented, but significant electrical power is wasted. Furthermore, if the thermistor for sensing the overheating of the recording elements is defective, the sheet of papers are continuously printed in black to consume the recording element and recording paper. In addition, when sheets of paper that are not printed but are supplied in blank due to occurrence of a problem on either the sending side or the receiving side of a telecommunication circuit, nothing is read from the blank sheet of paper during scanning, a waste of recording paper and an unnecessary increase in power consumption.
Exemplars of contemporary practice in the art are found in references such as U.S. Pat. No. 5,295,182 to Fujii, entitled Facsimile Device Having Self-Diagnostic Function And Maintenance And Control Method Thereof, U.S. Pat. No. 5,130,805 to Rikima, entitled Image Forming Apparatus With Detection And Indication Of Defective Image Data, U.S. Pat. No. 4,849,821 to Allen et al., entitled Page Check For Copier/Printer, U.S. Pat. No. 4,422,098 to Legie et al., entitled Internal Test Method And apparatus For Facsimile Transceiver, and U.S. Pat. No. 3,937,872 to Kondo et al., entitled Internal Test Method For Facsimile Transceiver. While I have observed that although these exemplars of the art might be read as advocating incorporation of self-diagnostic functions in facsimile machines, I have found that none of these references either recognizes the desirability of or provides an implementation for sensing abnormalities in data received during a receiving mode or in data read by scanning documents during a copy mode or transmitting mode.